The problem of malaria vector control in South Africa and southern Mozambique has recently become a serious issue. Compounding factors include the following. 1) Mozambique will not allow the use of DDT for house spraying and therefore will not achieve 100% eradication of the vector species An. funestus because of its resistance to the alternative insecticides. 2) DDT for house spraying was discontinued in South Africa because of global environmental pressure and because of objections raised by local communities to increased bed bug activity resulting from excitatory effects of DDT on the resistant bugs and to socially unacceptable residue marks on the walls of the houses. This was overcome by the introduction of pyrethroid spraying. By the end of summer 2000, South Africa had experienced its worst malaria epidemic for over 50 years and DDT was reintroduced. 3) Newly arisen resistance to DDT within populations of An. arabiensis in northern Kwazulu/Natal will likely accelerate replacement of DDT with other insecticides such as pyrethroids. As a result of the above, it is imperative that highly selective and sensitive, yet easy to use enzyme assays for pyrethroid-mediated resistance are developed. These assays are urgently needed to assess the extent of resistance in An. funestus and An. arabiensis and provide information on the most appropriate insecticidal treatment for resistance management. Research groups at the University of California at Davis have developed a series of novel reporters of enzyme-mediate resistance that have successfully been used in examining resistance in Culex mosquitoes. The overall objective of this study is to test these assays on resistant and susceptible strains of the African vectors An. funestus and An. arabiensis housed at the VCRU. We therefore propose the following specific objectives: 1. Adapt assays developed by UC Davis for the detection of enzyme-mediated pyrethroid resistance in Culex complex mosquitoes to An. funestus colonies and wild pyrethroid tolerant An. arabiensis. Evaluate novel rapid and sensitive fluorescent assays for mosquito pyrethroid selective esterase. B. Evaluate sensitive fluorescent assays for mosquito P450 mixed function oxidases. 2. Transfer these technologies to the VCRU and perform limited field trials in order to generate preliminary data that will enable the development of a full R01 application.